This study is designed to examine the relationship of genetic and autoimmune factors to the development and progression of diabetic retinopathy. Participants will be 440 randomly chosen insulin-dependent diabetic persons who are part of a well-characterized cohort in southern Wisconsin who were previously examined in 1980-1982. Participants will be examined in their home communities in a mobile examining van. As part of the evaluation, refraction, visual acuity, intraocular and blood pressure measurements according to standardized protocols, and determination of genetic factors (HLA: A, B, C. DR; Bf, Gm, Km, insulin gene (DNA) polymorphism), autoantibodies (to thyroglobulin, thyroid microsomal fraction, gastric parietal cell, and insulin), glycosylated hemoglobin level and plasma C-peptide levels will be performed. Objective recording of retinopathy by use of stereoscopic fundus photography combined with a standardized protocol for grading the retinopathy will be used. The relationship of the above described genetic and autoimmune factors and the incidence and progression of diabetic retinopathy will be evaluated controlling for known risk factors for diabetic retinopathy.